Death Valley gets less than 2 inches of rain a year, and summer temperatures can soar to 120 F or higher. Chances are that's one place you'd be sure to drink plenty of water.

But if you're in towns like Portland, Oregon; Cleveland; or New York City, where average highs are in the mid or upper 80s, you might not think hydration is much of a worry.

Gulp! That would be a mistake. Kidney specialists have discovered that in addition to all the standard symptoms of dehydration (cramping, heart palpitations, dizziness, infrequent urination and dark yellow urine), when temperatures jump to 86 F or higher, so does your risk of kidney stones.

So how much water should you drink when you're active on a hot day? Start with 16 ounces about an hour before you head out, and another glass 15 minutes right before you get going. Then drink 16 ounces every 30-60 minutes, depending on the temperature, your age, weight and activity. And you should urinate copiously 3-4 times a day; less indicates you're taking in too little liquid.

Also, replace electrolytes: Take a break to eat a banana (400 mg of potassium) and add a pinch of salt to your water if you're out for more than 90 minutes. Take in added calcium with nonfat, sugar-free yogurt, and at all times (except after you take a multivitamin!) your urine should be a pale, light, clear color. If it's dark and cloudy, start drinking cool water immediately. Stay clear of kidney stones in hot weather.